Research ArticleExperimental Studies
Open Access

Effect of Underwater Exercise on Salivary Metabolites of Older Persons With Disability

NOBUAKI TAMURA, KAZU MIZUNO, RYUICHIRO SUZUKI, MASAHIRO SUGIMOTO, AYAME ENOMOTO, SANA OTA, MIKU KANEKO, HIROSHI SAKAGAMI and HIROSHI TAKESHIMA
In Vivo November 2022, 36 (6) 2678-2688; DOI: https://doi.org/10.21873/invivo.13003

Abstract

Background/Aim: Underwater exercise is aimed at preventing aging, maintaining, and improving motor function, and improving physical function. However, its rehabilitation effects have not been well evaluated. In order to gain insight into the molecular basis of its rehabilitation effects, possible changes in the salivary metabolites of four older persons with disability (mean age: 72.5 years) during underwater exercise were investigated. Materials and Methods: Halitosis was measured by Breathtron; salivary bacterial number by bacterial counter; amino acids by amino acid analyzer; 8-oxoguanine by ELISA; and intracellular metabolites by capillary electrophoresis, time-of-flight mass spectrometry, liquid chromatography, and triode quadrupole mass spectrometry. Results: Underwater exercise induced apparent declines in two major salivary amino acids (glycine and proline) and bacterial numbers in the cheek mucosa and salivary, without apparent changes in the halitosis and urine 8-oxoguanine concentration. Older subjects showed higher concentrations of most of 166 metabolites compared to young volunteers (mean age: 38.8 years old). Fifteen compounds were significantly reduced with the progression of underwater exercise. Conclusion: Improvement of upright balance function with underwater exercise is correlated with several salivary components.

Key Words:

Developed countries have already entered into a super-aging society, making us deal with how to fill the gap between healthy lifespan and biological lifespan. Needless to say, to accomplish this, “prevention of diseases” and “prevention of frailty syndrome and long-term care” based on lifestyle-related diseases are important. Since the aging-associated decline in physical functions is also a physiological phenomenon, appropriate nutrition and exercise load are necessary, especially to combat the decline in the mass and strength of muscles.

It has become technically possible to simultaneously analyze the salivary metabolites by metabolome analysis. Recent reports suggest the possible link between salivary metabolites and oral (1) and general health (2) and between the salivary bacterial flora and health status (3, 4).

We have reported previously that age-associated increase in the salivary concentration of glycine (the most abundant amino acid) and lysine with aging, suggesting that these two amino acids can be considered as possible aging markers (5). Also, it has been reported that the pattern of salivary metabolites may be influenced by exercise (6-9). However, most of previous studies have focused on the elite athlete, rather than on the elderly, especially with disability.

PubMed survey (August 15, 2021) demonstrated the publication of 51 studies regarding the aquatic exercise of older people, and 85 studies about physiotherapy and underwater exercise. However, no study has been published on the effects of underwater exercise on salivary metabolites, halitosis, oral bacterial number, and aging marker. In the present small-scale trial, we preliminarily investigated whether underwater exercise improves these factors in four older subjects with lumbar stenosis, spinal canal stenosis, cervical disc herniated spine, and cerebral hemorrhage with right hemiplegia and if so, identify salivary components that might be responsible for the improvement.

Materials and Methods

Subjects. Physically malfunctioned older people usually stay in bed, use a wheelchair to move, or go to a rehabilitation center. Therefore, it was very difficult to collect large numbers of people who wish to participate in years-long experiments. Luckily, two males [subject 1 (74-year-old) and, subject 4 (66 years old)] and 2 females [subject 2 (78 years old) and subject 3 (73 years old)] (mean age 72.5 years) declared consent for participating in the underwater exercise therapy (indicated by a light blue color bar in Figure 1) in 2018. Before 6, 11, 6, and 3 years ago (that is; in the years of 2012, 2007, 2012, and 2015), subjects 1, 2, 3, and 4 could not walk due to heavy lumbar stenosis, spinal canal stenosis, cervical disc herniated spine, and cerebral hemorrhage with right hemiplegia, respectively, they had attended the pre-training (indicated by light yellow bars in Figure 1). On March 26, 2018, all of four participants became capable of walking in the pool, with support for subject 3. In the land, subjects 1, 2, and 3 became capable of walking 10 m, while subject 4 still needed the wheelchair. At that time, we started the underwater exercise therapy. At four time points thereafter [1st (a), 2nd (b), 3rd (c), and 4th], four subjects were tested for various parameters (March 2018~September 2019) (Figure 1). All four participants strictly adhered to the underwater training, under the guidance of Dr. Kazu Mizuno. First, saliva and urine were collected and frozen, and halitosis and bacteria number were measured in Meikai University Research Institute of Odontology (M-RIO). Then, four subjects moved to Josai University gymnasium (located 10 min walking distance from M-RIO). All experiments in the present study were conducted in coherence with the Declaration of Helsinki and the study was approved by the ethics committee of Meikai University School of Dentistry (approval no. A1709).

Figure 1.
Figure 1.

Protocol for underwater exercise therapy. During exercises (March 26, 2018~September 9, 2019), samples were taken at four different time points for the analysis [1st (June 18, 2018) (a), 2nd (September 10, 2018) (b), 3rd (April 15, 2019) (c) and 4th (September 9, 2019)].

Outline. Four subjects received the following balanced test and exercises (Borg scale: 9-10; total 45-60 min) in the swimming pool (space: 25 m×13 m; depth: 1.2 m; water temperature: 32±1°C), twice a week throughout experimental periods.

Balance test. Standing on tiptoes (30-s×3 times): With eyes closed or open, spread both hands on one leg and stand on one leg to see how many seconds the subjects can hold. In general, it can be maintained for 30-40 s.

Exercises. The following four tests were performed (i) Squat (30-s×5 times), (ii) Walking in the poolside (25 m×3 times) <rested 5 min>, (iii) Underwater walking without support: 25 m×4 times <rested 5 min>; (iv) Floating in a backstroke fashion for 3 min×3 times.

Assay of halitosis. Breath was collected for 45 s through a mouthpiece, and the concentration of volatile sulfur compounds (VSCs) in the breath was measured by the commercially available Breathtron [150 mm (W)×150 mm (H)×230 mm (D)] (Yoshida Co., Ltd., Tokyo, Japan) and recorded in parts per billion (ppb), according to the instructions of the manufacturer (10). Each volunteer was subjected to repeated measurements 3 times for the calculation of the mean value.

Assay of bacterial number. Bacteria on the center of the dorsum of the tongue were gently scraped off by cotton swab (three strokes) and immersed in 5 ml of water in a disposable cup, and the number of bacteria was determined by a bacteria counter [144 mm (W)×147 mm (H)×189 mm (D)] (Panasonic Healthcare Co. Ltd., Tokyo, Japan), according to the instructions of the manufacturer (10). Each volunteer was subjected to repeated measurements 3 times for the calculation of the mean value.

Amino acids determination. Whole saliva was collected into a beaker for 5 min in the daytime (10:00-11:00 or 14:00-15:00). Saliva (0.1 ml) was mixed with 0.1 ml of 10% trichloroacetic acid (Wako Pure Chem Co., Tokyo, Japan). After centrifugation for 5 min at 21,000×g at 4°C, the deproteinized supernatant was collected and stored at −30°C. The supernatants (20 μl) were subjected to a JLC-500/V amino acid analyzer (JEOL, Tokyo, Japan) and amino acids were detected by the ninhydrin reaction (5).

Determination of 8-oxoguanine. Urine was corrected and immediately frozen and urinary 8-oxoguanine was measured by ELISA [Japan Institute for the Control of Aging (JaICA), NIKKEN SEIL. Co., Ltd., Shizuoka, Japan].

Metabolomic analysis. Eight normal volunteers (6 males and 2 females, mean ages 38.8 years old) without joining the underwater exercise, kindly provided their saliva for use as a control level of salivary components. Frozen saliva was thawed and filtered through a 5-kDa cut-off filter (Millipore, Bedford, MA, USA) at 9,100×g for at least 2.5 h at 4°C to remove macromolecules. The metabolomic analysis of saliva samples was conducted following the protocol (11, 12).

For capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) analysis, sample (45 μl) was then aliquoted into a 1.5-ml Eppendorf tube (Sigma-Aldrich, St. Louis, MO, USA) along with 2 mM of internal standards including methionine sulfone, 2-[N-morpholino]-ethanesulfonic acid, d-camphol-10-sulfonic acid, sodium salt, 3-aminopyrrolidine, and trimesate.

For liquid chromatography-triple-quad MS (LC-QQQMS) analysis, saliva sample (10 μl) was mixed with methanol (30 μl) containing 149.6 mM ammonium hydroxide (1% (v/v) ammonia solution) and 2.5 μM internal standards (d8-spermine, d8-spermidine, d6-N1-acetylspermidine, d3-N1-acetylspermine, d6-N1,N8-diacetylspermidine, d6-N1, N12-diacetylspermine, hypoxanthine-13C,15N, and 1,6-diaminohexane). After centrifugation at 15,780×g for 10 min at 4°C, the 30 μl supernatant was transferred to another tube, mixed with 50 μl water, and centrifuged at 15,780×g for 10 min at 4°C, and then 1 μl of the supernatants were subjected to LC-QQQMS (11, 12).

The data processing processes of these MS data were described elsewhere (11). Briefly, the process starts from the data conversion from the vendor-supplied format file to a readable one. Peaks were detected and integrated to calculate the peak area, and this value was divided by the one of internal standard (relative peak area), to eliminate the unexpected bias caused by the fluctuation of mass sensitivity. The migration times of each peak were corrected and peak matching across multiple datasets was conducted. For each metabolite, the ratio of the relative peak area in each sample and standard mixture was used to calculate the absolute metabolite concentration in saliva samples. Before measuring samples, the standard mixtures of various dilutions were analyzed and the lower and upper limits of linearity between metabolite concentration and peak area were confirmed. The peaks under the lower limit were considered as not detected and 0 was substituted and the peaks over the upper limit were considered as saturated peaks.

Data analysis. Metabolite concentrations were visualized in heatmaps. To eliminate the bias of the overall concentration of saliva, the concentration of each metabolite was divided by the averaged concentration of the metabolite. To visualize these data in color representation, each value was transferred to Z-score. Otherwise, to visualize the relative concentration compared to the first time point, each metabolite concentration was divided to that of the first point, to yield the fold change (F.C.). In each heatmap, blue (relatively low), red (relatively high), and while (average) were assigned. To evaluate the similarity of the metabolite concentration patterns among the saliva samples, metabolites were clustered using Pearson’s correlation. To assess the change in metabolite concentrations during time, Freidman test was used.

Data analyses were performed using the GraphPad Prism software (v.8.4.3; GraphPad Software, San Diego, CA, USA), Mev TM4 (v4.9.0) (13), and BellCurve for Excel (Social Survey Research Information Co., Ltd., Tokyo, Japan). For heatmap visualization. Differences with a p<0.05 were considered statically significant.

Results

Rehabilitation effects of underwater exercise. Three subjects, 1-3, were tested for the standing balance function, assessed by the eye-opening time and eye closing time during 1 min of underwater exercise (Table I). Eye-opening reflects the level of balance due to the elevation of cognitive function through visual information. Eye closing reflects the operation ability level by somatosensory memory. Water exercise increased both the eye-opening time and eye closing time, suggesting the restoration of cognitive function and improvement of balance control function, rather than simply the learning effect (Table I). We have not conducted a one-legged standing test for subject 4, who cannot stand on one leg, due to the cerebral hemorrhage and right hemiplegia. Based on the capability of walking on one-leg, we included subjects 1-3 and excluded subject 4 in this test.

View this table:
Table I.

Improvement in eye-opening and closing by underwater exercise.

Subjects 1-3 were tested for forward, sideways, or backward walking in the pool, assessed by the time required for walking 25 m (that reflects muscle function) and the number of steps (that reflects movement function) (Table II). We confirmed that sideward walking was the fastest due to the less frontal resistance in the water. Interestingly, we found that underwater exercise improved the backward walk (assessed by faster walk and increased stride), but not the forward and sideways walk. This may relate to the fact that a backward walk is an action that is not performed daily. On the contrary, underwater excise improved forward, sideways, and backward walks in subject 4. Underwater exercise affected muscle and movement functions differently, from satisfactorily to unsatisfactorily: Subject 4>subject 1>subject 2>subject 3.

View this table:
Table II.

Effect of underwater exercise on muscle and movement functions.

Effect of underwater exercise on salivary amino acids, halitosis, and oral bacterial number. An automatic amino acid analyzer is a robust analytical instrument, providing highly reproducible data. The basic principle of analysis is the same as that of HPLC, in which amino acids separated by a cation exchange resin are derivatized with a ninhydrin reagent and then detected by a visible light detector. We collected the saliva of subjects who underwent underwater exercise, deproteinized them by addition of trichloroacetic acid and centrifugation, and then subjected them to a fully automatic amino acid analyzer (JLC-500, JEOL). Salivary glycine and proline were present in concentrations up to 675 and 656 μM, respectively. Although fluctuated profoundly from subject to subject, the salivary concentration of glycine and proline declined in all cases (to 41~99% and 12~45% of control level, respectively) (Figure 2A and B). However, the urinary 8-oxoguanine concentration was kept between 71 to 114% of the control level, during water exercise (Figure 2C). Since subject 4 could walk underwater, it was judged that he had the same ability as the other three and therefore, he was also included in this test.

Figure 2.
Figure 2.

Water exercise affected more profoundly the concentration of salivary glycine and proline than that of urinary 8-oxoguanine in the four subjects. 1st (Jun 2018) (a), 2nd (Sep 2018) (b), 3rd (Apr 2019) (c) and 4th (Sep 2019).

We investigated the effect of underwater exercise on the numbers of non-specified bacteria in the oral cavity. Oral bacteria are most abundant on the tongue, followed by saliva and cheek mucosa (Table III). With the progression of underwater exercise, the bacteria in the tongue did not change significantly (p=0.86). However, bacteria in the cheek mucosa and saliva declined to 1/3 or 1/9 after the 1st underwater exercise, but not significantly (p=0.07, p=0.21) (Table I). Underwater exercise did not significantly reduce the halitosis of the four subjects (p=0.37) (Table IV).

View this table:
Table III.

Effect of water exercise on the oral bacterial number.

View this table:
Table IV.

Effect of water exercise on halitosis.

Age-related increase in salivary metabolites. Metabolomic analyses identified and quantified 191 metabolites, and, of these, 61 metabolites detected in more than 50% of samples were used for the subsequent analyses. The concentrations of salivary metabolites were divided by the mean of all samples (young volunteers+older subjects), and almost all metabolites in young volunteers were below the average (indicated blue color), regardless of the collection time of saliva, either morning (AM) or afternoon (PM). On the other hand, many metabolites of older subjects were higher than the average of all samples (indicated by red color) (Figure 3A). These points became much clearer when the salivary concentration of each metabolite was expressed as the ratio to the mean of young volunteers (Figure 3B).

Figure 3.
Figure 3.
Figure 3.

Comparison of the concentrations of salivary metabolites between young volunteers and older subjects. Saliva was collected from 8 young volunteers (upper) in the morning (AM) and afternoon (PM), and four older subjects in the morning, at the 1st, 2nd, 3rd, and 4th underwater exercise. Salivary concentration was divided by the means of all samples (A) and the means of young volunteers (B). Blue, white, and red colors indicate low, average, and higher concentrations, respectively. 1st (Jun 2018) (a), 2nd (Sep 2018) (b), 3rd (Apr 2019) (c) and 4th (Sep 2019).

Effect of water exercise on salivary metabolites. When the salivary concentrations of each compound were normalized with those of the first underwater exercise, many compounds in the zone indicated by the red bracket declined with the progression of underwear exercise (Figure 4).

Figure 4.
Figure 4.

Changes in the concentration of several salivary metabolites in four older subjects during underwater exercise, normalized by the data of the first exercise. Color indicates the fold change. Gray indicates the peaks under the lower limit (not detected) in the case of agmatine, making the denominator of “zero”, and over the upper limit (saturated) in the case of urocanate and glutamine, as described in Materials and Methods. The concentrations of each sample are divided by those of the samples labeled with “-1”. 1st (June 18, 2018) (a), 2nd (September 10, 2018) (b), 3rd (April 15, 2019) (c), and 4th (September 9, 2019).

We found that metabolites indicated by the red bracket were increased during aging and then declined by repeated underwater exercise (Figure 5). Especially, three compounds surrounded by the green box (agmatine, beta-alanine, and sarcosine) declined up to a level lower than that of young volunteers (Figure 5). Fifteen metabolites that significantly declined by underwater exercise are shown in Figure 6.

Figure 5.
Figure 5.

Averaged value of each group of Z-score converted metabolite concentrations. Underwater exercise reduced the levels of three compounds (agmatine, beta-alanine, and sarcosine) to below those of younger patients (green box). 1st (Jun 2018) (a), 2nd (Sep 2018) (b), 3rd (Apr 2019) (c), and 4th (Sep 2019).

Figure 6.
Figure 6.

Salivary metabolites that were significantly reduced during repeated underwater exercise. Friedman test (matched, nonparametric) was used. The X-axis indicates the times of underwater exercise. *p<0.05 and **p<0.01. 1st (Jun 2018) (a), 2nd (Sep 2018) (b), 3rd (Apr 2019) (c), and 4th (Sep 2019).

Lastly, we compared the improvement in physical functions during Jun 2018 to Apr 2019 and salivary metabolic profiles. We found that the improvement in balance function was related to the decline in six metabolites (agmatine, adenine, beta-alanine, sarcosine, benzoate, phosphorylcholine). However, the underwater walking capability was only improved in subject 4, suggesting that the decrease in glycine and GABA was mostly correlated to the improvement in walking capability (Figure 7).

Figure 7.
Figure 7.

Correlation of the improvement in underwater capability and changes in salivary metabolites. Heatmap data of changes from 1st (Jun 2018) (a) to 3rd (Apr 2019) (c), derived from Table I. On the right panel, red, blue, and yellow indicate elevation, reduction, and no change, respectively.

Discussion

The present study demonstrated that underwater exercise reproducibly increased eye-opening and closing (Table I), suggesting the improvement in the sense of balance by reducing the wobbling. Since most of the informational recognition is done by vision, this result suggests the beneficial effects of underwater exercise. We also found that underwater exercise improved the muscle and movement function (assessed by increases of both the walking speed and length of stride), only in the backward walk, but not in the forward and sideway walk (Table II). This may relate to the fact that a backward walk is an action that is not performed daily. On the contrary, underwater exercise improved all forward, sideways, and backward walks in older subjects with cerebral hemorrhage with right hemiplegia (subject 4). This suggests that underwater exercise may have improved the symptoms of right hemiplegia.

The present study demonstrated that underwater excise did not significantly change the number of oral bacteria (Table III), but reduced the salivary concentration of the most abundant amino acids (glycine, proline) (determined by the amino acid analyzer in Figure 2) and other 15 metabolites (agmatine, beta-alanine, benzoate, betaine, cadaverine, carnitine, DHAP, gamma-butyro-betaine, hexanoate, N-acetylputrescine, phosphorylcholine, sarcosine, serine, threonine, urate) (determined by metabolome analysis in Figure 6). This phenomenon may be explained by a significant reduction in saliva flow rate during aging (14, 15), and by the reversal of saliva flow by the exercise (excise has been reported to increase the saliva flow rate (16, 17). Salivary secretion is evoked by cholinergic parasympathetic and adrenergic sympathetic autonomic nerves (18), which may be stimulated by underwater exercise. We have previously reported that glycine and proline are present in the saliva at millimolar concentrations (5). We found here that underwater exercise reduced glycine and proline only by 50% in older people with a history of severe diseases. The biological significance of the considerable reduction in these amino acids after exercise should be clarified.

Finally, we investigated the correlation between the improvement in underwater capability and changes in salivary metabolites (Figure 7). Heatmap data of changes from 1st (Jun 2018) (a) to 3rd (Apr 2019) (c) demonstrated that approximately 1/4 of salivary metabolites increased during underwater exercise, and there were variations in response to exercise from subject to subject. However, the improvement in balance function was related to the decline in six metabolites (agmatine, adenine, beta-alanine, sarcosine, benzoate, phosphorylcholine). Furthermore, underwater exercise did not affect the urinary concentration of 8-oxoguanine, one of the aging markers (19, 20) (Figure 2C), and halitosis (Table III). This suggests that underwater exercise alone may not reverse the aging process.

The present preliminary study was performed using limited numbers of subjects and an inappropriate choice of control due to the difficulty in finding a younger population with the same diseases that older people have. Securing higher numbers of older people with severe diseases who are willing to participate in this long-year study are necessary. Large-scale studies will clarify the reproducibility and whether the phenomena observed in this study are reversible or irreversible after the termination of the underwater exercise.

Acknowledgements

The Authors acknowledge the four older subjects and eight young volunteers who provided saliva, used as controls in the present study. This research was partially supported by KAKENHI from the Japan Society for the Promotion of Science (JSPS), grant number 17K12055 (N.T.), grant number 20H05743 (M.S.).

Footnotes

  • Author’s Contributions

    NT and KM performed most of the experiments of the present study. RS performed the amino acid analysis. AE, SO, and MK performed the metabolome analysis. MS performed data analysis. NT, HS, and MS wrote, reviewed, interpreted the experimental results, and edited the manuscript. All Authors read and approved the final version of the manuscript.

  • Conflicts of Interest

    The Authors wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.

  • Received August 15, 2022.
  • Revision received August 29, 2022.
  • Accepted September 2, 2022.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY-NC-ND) 4.0 international license (https://creativecommons.org/licenses/by-nc-nd/4.0).

References

  1. ↵
    1. Liebsch C,
    2. Pitchika V,
    3. Pink C,
    4. Samietz S,
    5. Kastenmüller G,
    6. Artati A,
    7. Suhre K,
    8. Adamski J,
    9. Nauck M,
    10. Völzke H,
    11. Friedrich N,
    12. Kocher T,
    13. Holtfreter B and
    14. Pietzner M
    : The saliva metabolome in association to oral health status. J Dent Res 98(6): 642-651, 2019. PMID: 31026179. DOI: 10.1177/0022034519842853
    OpenUrlCrossRefPubMed
  2. ↵
    1. Zhang A,
    2. Sun H and
    3. Wang X
    : Saliva metabolomics opens door to biomarker discovery, disease diagnosis, and treatment. Appl Biochem Biotechnol 168(6): 1718-1727, 2012. PMID: 22971835. DOI: 10.1007/s12010-012-9891-5
    OpenUrlCrossRefPubMed
  3. ↵
    1. Belstrøm D
    : The salivary microbiota in health and disease. J Oral Microbiol 12(1): 1723975, 2020. PMID: 32128039. DOI: 10.1080/20002297.2020.1723975
    OpenUrlCrossRefPubMed
  4. ↵
    1. Sugimoto M
    : Salivary metabolomics for cancer detection. Expert Rev Proteomics 17(9): 639-648, 2020. PMID: 33140667. DOI: 10.1080/14789450.2020.1846524
    OpenUrlCrossRefPubMed
  5. ↵
    1. Tanaka S,
    2. Machino M,
    3. Akita S,
    4. Yokote Y and
    5. Sakagami H
    : Changes in salivary amino acid composition during aging. In Vivo 24(6): 853-856, 2010. PMID: 21164043.
    OpenUrlAbstract/FREE Full Text
  6. ↵
    1. Pintus R,
    2. Bongiovanni T,
    3. Corbu S,
    4. Francavilla VC,
    5. DessÌ A,
    6. Noto A,
    7. Corsello G,
    8. Finco G,
    9. Fanos V and
    10. Cesare Marincola F
    : Sportomics in professional soccer players: metabolomics results during preseason. J Sports Med Phys Fitness 61(2): 324-330, 2021. PMID: 32936572. DOI: 10.23736/S0022-4707.20.11200-3
    OpenUrlCrossRefPubMed
    1. Bazzano M,
    2. Laghi L,
    3. Zhu C,
    4. Lotito E,
    5. Sgariglia S,
    6. Tesei B and
    7. Laus F
    : Exercise induced changes in salivary and serum metabolome in trained standardbred, assessed by 1H-NMR. Metabolites 10(7): 298, 2020. PMID: 32708237. DOI: 10.3390/metabo10070298
    OpenUrlCrossRefPubMed
    1. Bongiovanni T,
    2. Pintus R,
    3. Dessì A,
    4. Noto A,
    5. Sardo S,
    6. Finco G,
    7. Corsello G and
    8. Fanos V
    : Sportomics: metabolomics applied to sports. The new revolution? Eur Rev Med Pharmacol Sci 23(24): 11011-11019, 2019. PMID: 31858572. DOI: 10.26355/eurrev_201912_19807
    OpenUrlCrossRefPubMed
  9. ↵
    1. Akazawa N,
    2. Kobayashi N,
    3. Nakamura Y,
    4. Kumagai H,
    5. Choi Y and
    6. Maeda S
    : Effect of sleep efficiency on salivary metabolite profile and cognitive function during exercise in volleyball athletes. Eur J Appl Physiol 119(10): 2215-2223, 2019. PMID: 31407087. DOI: 10.1007/s00421-019-04205-7
    OpenUrlCrossRefPubMed
  10. ↵
    1. Sakagami H,
    2. Sheng H,
    3. Ono K,
    4. Komine Y,
    5. Miyadai T,
    6. Terada Y,
    7. Nakada D,
    8. Tanaka S,
    9. Matsumoto M,
    10. Yasui T,
    11. Watanabe K,
    12. Junye J,
    13. Natori T,
    14. Suguro-Kitajima M,
    15. Oizumi H and
    16. Oizumi T
    : Anti-halitosis effect of toothpaste supplemented with alkaline extract of the leaves of Sasa senanensis Rehder. In Vivo 30(2): 107-111, 2016. PMID: 26912820.
    OpenUrlAbstract/FREE Full Text
  11. ↵
    1. Sugimoto M,
    2. Ota S,
    3. Kaneko M,
    4. Enomoto A and
    5. Soga T
    : Quantification of salivary charged metabolites using capillary electrophoresis time-of-flight-mass spectrometry. Bio Protoc 10(20): e3797, 2020. PMID: 33659451. DOI: 10.21769/BioProtoc.3797
    OpenUrlCrossRefPubMed
  12. ↵
    1. Nakajima T,
    2. Katsumata K,
    3. Kuwabara H,
    4. Soya R,
    5. Enomoto M,
    6. Ishizaki T,
    7. Tsuchida A,
    8. Mori M,
    9. Hiwatari K,
    10. Soga T,
    11. Tomita M and
    12. Sugimoto M
    : Urinary polyamine biomarker panels with machine-learning differentiated colorectal cancers, benign disease, and healthy controls. Int J Mol Sci 19(3): 756, 2018. PMID: 29518931. DOI: 10.3390/ijms19030756
    OpenUrlCrossRefPubMed
  13. ↵
    WebMeV. Available at: http://mev.tm4.org/ [Last accessed on August 30, 2022]
  14. ↵
    1. Li L,
    2. Wang H,
    3. Hu L,
    4. Wu X,
    5. Zhao B,
    6. Fan Z,
    7. Zhang C,
    8. Wang J and
    9. Wang S
    : Age associated decrease of sialin in salivary glands. Biotech Histochem 93(7): 505-511, 2018. PMID: 29790791. DOI: 10.1080/10520295.2018.1463453
    OpenUrlCrossRefPubMed
  15. ↵
    1. Smith DJ,
    2. Joshipura K,
    3. Kent R and
    4. Taubman MA
    : Effect of age on immunoglobulin content and volume of human labial gland saliva. J Dent Res 71(12): 1891-1894, 1992. PMID: 1452889. DOI: 10.1177/00220345920710120701
    OpenUrlCrossRefPubMed
  16. ↵
    1. Leicht CA,
    2. Goosey-Tolfrey VL and
    3. Bishop NC
    : Exercise intensity and its impact on relationships between salivary immunoglobulin A, saliva flow rate and plasma cortisol concentration. Eur J Appl Physiol 118(6): 1179-1187, 2018. PMID: 29627864. DOI: 10.1007/s00421-018-3847-6
    OpenUrlCrossRefPubMed
  17. ↵
    1. Rutherfurd-Markwick K,
    2. Starck C,
    3. Dulson DK and
    4. Ali A
    : Salivary diagnostic markers in males and females during rest and exercise. J Int Soc Sports Nutr 14: 27, 2017. PMID: 28811748. DOI: 10.1186/s12970-017-0185-8
    OpenUrlCrossRefPubMed
  18. ↵
    1. Proctor GB
    : The physiology of salivary secretion. Periodontol 2000 70(1): 11-25, 2016. PMID: 26662479. DOI: 10.1111/prd.12116
    OpenUrlCrossRefPubMed
  19. ↵
    1. Ba X,
    2. Aguilera-Aguirre L,
    3. Rashid QT,
    4. Bacsi A,
    5. Radak Z,
    6. Sur S,
    7. Hosoki K,
    8. Hegde ML and
    9. Boldogh I
    : The role of 8-oxoguanine DNA glycosylase-1 in inflammation. Int J Mol Sci 15(9): 16975-16997, 2014. PMID: 25250913. DOI: 10.3390/ijms150916975
    OpenUrlCrossRefPubMed
  20. ↵
    1. Jacob KD,
    2. Noren Hooten N,
    3. Trzeciak AR and
    4. Evans MK
    : Markers of oxidant stress that are clinically relevant in aging and age-related disease. Mech Ageing Dev 134(3-4): 139-157, 2013. PMID: 23428415. DOI: 10.1016/j.mad.2013.02.008
    OpenUrlCrossRefPubMed
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Effect of Underwater Exercise on Salivary Metabolites of Older Persons With Disability
NOBUAKI TAMURA, KAZU MIZUNO, RYUICHIRO SUZUKI, MASAHIRO SUGIMOTO, AYAME ENOMOTO, SANA OTA, MIKU KANEKO, HIROSHI SAKAGAMI, HIROSHI TAKESHIMA
In Vivo Nov 2022, 36 (6) 2678-2688; DOI: 10.21873/invivo.13003
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